Electric circuit breaker with positive tripping means



Oct. 26, 1965 M. F. KOENlG ETAL 3,214,535

ELECTRIC CIRCUIT BREAKER WITH POSITIVE TRIPPING MEANS Filed Feb. 27,1963 2 She ets-Sheet 1 Oct. 26, 1965 M. F. KOENIG ETAL 3,214,535

ELECTRIC CIRCUIT BREAKER WITH POSITIVE TRIPPING MEANS Filed Feb. 27,1963 2 Sheets-Sheet 2 United States Patent 3,214,535 ELECTRIC CIRCUITBREAKER WITH POSKTIVE TRIPPING MEANS Martin F. Koenig and Alexander J.Pastene, Milwaukee, and Lloyd D. Williams, Waukesha, Wis., assignors toCutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware FiledFeb. 27, 1963, Ser. No. 261,345 11 Claims. (Cl. 200-458) This inventionrelates to electric circuit breakers and more particularly to electriccircuit breakers of the thermal and magnetic trip type.

This invention, although not limited thereto, is especially applicableto circuit breakers of the type having an overcenter spring mechanismfor tripping the breaker to open-circuit condition and having a latchwhich is held in engagement with the overcenter spring mechanism andwhich is disengaged to trip the breaker in response to an abnormalelectrical condition, such as disclosed in Martin F. Koenig, AlexanderJ. Paste-x1e and Lloyd D. Williams copending application Serial No.1,073, filed January 7, 1960, Patent -No. 3,081,386, dated March 12,1963, and assigned to the assignee of this invention.

An object of the invention is to provide an improved circuit breaker.

A more specific object of the invention is to provide an improvedtripping mechanism for a circuit breaker of the thermal and magnetictrip type.

Another specific object or the invention is to provide a circuit breakerwith improved means for positively causing tripping thereof in responseto an abnormal or excessive current condition.

Another object of the invention is to provide a circuit breaker withimproved operating mechanism which allows use of less expensive materialparticularly for the latch parts because mechanical deterioration orcorrosion products occurring over a period or time will not affect theoperating characteristics thereof.

Other objects and advantages of the invention will hereinafter appear.

According to the invention, there are provided improvements to a circuitbreaker of the type disclosed in the aforementioned Koenig et .al.patent whereby the breaker is positively caused to trip to open-circuitcondition when an abnormal current condition occurs. 'These improvementscomprise the addition of a latch hook whereby the latch is positively orforcibly separated from the catch under excessive thermal or magneticaction. This latch hook is secured to the armature and moves therewithto pull the latch away from the catch. These improvements also compriselateral slots forming a pair of inwardly directed projections on theslide plate confining the end of the armature so that when theelectro-responsive thermal element bends and moves the slide plate, thelatter forcibly moves the armature to .cause tripping of the breaker.Since the latch is actually pulled away from the catch to trip thecircuit breaker, corrosion on the catch will not alfect or change theoperating characteristics over a period of time.

7 These and other objects and advantages of the invention and the mannerof obtaining them will best be understood by reference to the followingdetailed description of an embodiment of the invention taken inconjunction with the accompanying drawings, wherein:

FIGURE 1 is a fragmentary front elevational view with the cover removedof a circuit breaker constructed in accordance with the invention andshowing the breaker mechanism in its on condition;

FIG. 2 is :an isometric view of the armature assembly and slide plate ofthe breaker of FIG. 1;

FIG. 3 is a front elevational view like FIG. 1 but showing the breakermechanism in its tripped or off condition; and

FIG. 4 is a front elevational view like FIGS. 1 and 3 but showing thebreaker mechanism in a transistory condition following tripping butbefore resetting of the latch.

Referring to FIG. 1, there is shown one pole of a plural pole circuitbreaker having a shallow insulating housing 2 provided with an openfront which may be closed by a cover. Housing 2 is provided at its topwith an aperture 2a through which extends the handle portion 4a of anoperating lever 4. The operating lever is provided with a pair ofcylindrical projections 4b integral therewith and laterally extendingtherefrom in opposite directions whereby the operating lever isjournaled in the housing .and cover for rotation through a limited arc.'llhe midportion 4c of the operating lever is enlarged and partiallyrounded so that as the handle is rotated from its extremecounterclockwise on position shown in FIG. 1 to its extreme clockwiseoff or tripped position shown in FIG. 3, such enlarged midp-ort-ionmaintains aperture 2a closed at all times.

The lower portion 4d of the operating lever is enlarged .and dividedinto two leg portions to provide space for pivotal excursion of a triplever or latch lever 6 therebetween and to provide for pivotalsuspension of a latch 8 and a movable contact 10 therefrom.

Latch lever 6 is generally of inverted U-shaped configuration and ispivoted at the lower end of the left depending leg thereof at a fixedpoint in a recess in housing 2. An over-center tension spring 12 has oneend h-ook connected in a hole in the yoke portion intermediate the legsof the latch lever. The other end hook of overcenter spring 12 isconnected in a hole in the lower end of movable contact carrier orfinger 10 having a contact 10a thereon. The upper end of movable contactfinger 10 is bifurcated and the bifurcated ends 10b are bent outwardlyin opposite directions and extend into holes in the divided lowerportions 4d of the operating lever to pivot the movable contact fingeron the operating lever. *It will be apparent from the foregoingdescription that Whenever the operating lever moves the movable contactfinger pivot and the center line or line of action of the overcenterspring across one another, the movable contact finger will snap open orclosed relative to stationary contact 14 depending upon the direction ofmovement. Also, when latch lever 6 is released to move the upper end ofthe overcenter spring past the movable contact finger pivot, the movablecontact finger will snap open relative to the stationary contact.

A tension spring 16 has one end hook connected in a hole in the leftdepending leg of latch lever 6 and has its other end hook connected to astationary projection 18 molded integrally in the housing. Spring 16 isa resetting spring which rotates the latch lever counterclockwisewhenever overcenter spring 12 is relaxed and does not overpower thesame. A connector 14a is connected to the stationary contact and extendsthrough an aperture in the lower portion of the housing to affordelectrical connection of the breaker to an external circuit. A commontrip lever 20 is journaled in holes extending through the housing andcover below the right-hand depending leg of latch lever 6 to causetripping of a second, adjacent breaker when the first breaker trips.Latch 8 is U-shaped and the upper ends 8a of the side portions thereofare bent outwardly in opposite directions and are journaled in alinedholes in the divided portions 4d of the operating lever to freely pivotthe latch on the operating lever. The lower yoke portion of latch 8 isprovided with aflat upper surface 811 inclined at a small angle to theleft for engagement on a catch 6a provided on the right-hand'depending I3 leg portion of latch lever 6, this catch being most clearly shown inFIG. 4.

A slide plate 22 is slidably accommodated in horizontal slots in thehousing and cover and is biased in the lefthand direction by a helicalcompression spring 24 positioned between a Wall of the housing and theright-hand end portion of the slide plate. To maintain spring 24 inregistration with the slide plate, the latter is provided with spacednotches providing a tongue 22a therebetween as shown in FIG. '2. Asshown in FIG. 1, the opposite sides of spring 24 are in these notchesand tongue 22a extends into the left-hand end of the spring to maintainthe slide plate in engagement with the spring.

As shown in FIG. 2, the left-hand end of slide plate 22 is provided witha slot 22b for accommodating the lower free end of a thermal elementsuch as bimetal element 26. The upper end of bimetal element 26 isrigidly secured as by welding to the upper end of an electricalconnector member 28. Connector member 28 is held in a slot in thehousing formed partly by the right-hand Wall portions of the housing andis held in position by an adjusting screw 30. Screw 30 extends from theexterior of the housing through a slot in the right-hand wall thereofthrough a hole in connector member 28 into threaded engagement with atapped hole in a pole piece hereinafter described. The right-hand wallof the housing above and below screw 30 is provided with an undercutportion 2b to afford adjustment of the position of bimetal element 26 bybending connector member 28 when screw 30 is turned in while the head ofthe screw bears against the exterior wall of the housing. The lower endof connector member 28 extends through an aperture in the righthand wallof the housing and is provided with a screw type connector or the liketo afford connection thereof to an external circuit.

An elongated fiat armature 32 is provided at its upper end portion withrearwardly and forwardly projecting ears 32a shown in FIG. 2 forpivotally supporting the armature in depressions in the housing andcover as shown in FIG. 1. The rearward and forward edges of slot 22b inslide plate 22 are provided with laterally alined slots 220 foraccommodating the lower end portion of armature 32. As a result of theforce of spring 24 acting through slide plate 22, the lower end ofarmature 32 is biased in the left-hand direction and is moved in theright-hand direction by projections 22d on slide plate 22 when bimetalelement 26 bends.

A compensating bimetal element 34 is rigidly secured as 'by welding atits lower end portion to the left-hand surface of the lower end portionof armature 32. The upper portion of compensating bimetal element 34diverges from armature 32 into engagement with the lower end portion oflatch 8 so as to normally press latch 8 into engagement with catch 6a onthe latch lever. A latch hook 36 preferably of resilient spring wire butwhich could be rigid is rigidly secured as by welding at its upper endportion to the left-hand surface of the upper portion of armature 32.Latch hook 36 extends at an angle from the armature in the left-handdownward direction and its lower end portion is bent downwardly intoengagement with and overlapping the upper tip portion of compensatingbimetal element 34. The lower end of latch hook 36 is arranged so thatwhen the breaker is turned from its 01f position shown in FIG. 3 to itson position shown in FIG. 1, the lower yoke portion of U-shaped latch 8enters between compensating bimetal element 34 and latch hook 36 andseparates the latter from the former against the spring bias of thelatch hook. As shown in FIG. 2, latch hook 36 is positioned and securedoff-center relative to the upper end of compensating bimetal element 34and armature 32 so that it can enter on one side of the right-handdepending leg of latch lever 6 and will not interfere with movement ofthe latch lever.

A magnetiza'ble pole piece 38 of generally rectangular blockconfiguration is positioned on the right-hand side of bimetal element 26for magnetically attracting armature 32 which is positioned on theleft-hand side of bimetal element 26 substantially parallel to thelatter. Pole piece 38 is provided with a tapped hole into which theextreme end portion of adjusting screw 30 is threaded to maintain thepole piece at a downwardly diverging angle to bimetal element 26 wherebyto afford space for the lower end of bimetal element 26 to bend in theright-hand direction. The right-hand surface of pole piece 38 isprovided with a pair of elongated extrusions 38a, one on each side ofthe adjusting screw hole therein which bear against connector member 28to space the remainder of the pole piece from the latter. An L-shapedinsulating strip 40 has one angular portion anchored between connector14a and a horizontal wall of the housing by way of a hole in such stripand a projection 20 molded in such wall of the housing. The otherangular portion of the insulating strip extends upwardly to provideeffective dielectric protection of contact finger 10 from the left-handdepending leg of latch lever 6. A pair of electrical conductors 42connect the lower end portion of bimetal element 26 to movable contactfinger 10.

FIG. 3 shows the breaker in its tripped or 01f condition. When themanual operating lever is rotated in the counterclockwise direction, theupper pivot of contact finger 10 at the lower left-hand portion of theoperating lever is moved in the right-hand direction toward the centerline or line of action of overcenter spring 12. At the same time, thelower right-hand portion of the operating lever raises latch 8 so thatthe lower horizontal yoke portion of the latch engages catch 6a on thelatch lever. Following engagement of the catch by the latch, furtherrotation of the operating lever causes latch 8 to rotate latch lever 6counterclockwise. As a result, the latch lever moves the upper end ofspring 12 and the line of action of this spring in the left-handdirection. When the contact finger pivot and the line of action of theovercenter spring pass one another, the overcenter spring causes thecontact finger to pivot whereby to snap the movable contact intoengagement with the stationary con tact as shown in FIG. 1. In thisposition of the breaker, the lower horizontal portion 8b of latch 8 hasentered between latch hook 36 and compensating bimetal element 34 andhas separated the latch hook from the latter.

In the closed condition of the breaker shown in FIG. 1, compressionspring 24 biases slide plate 22 in the left-hand direction. The slideplate acts upon the lower end portion of armature 32 to cause the upperend of compensating bimetal element 34 to apply a force against thelower end of latch 8 whereby the latch is maintained in engagement withthe catch on the latch lever. Latch hook 36 is preferably made of springmetal rather than being stiff so that the lower end thereof will be inengagement with the latch to eliminate lost motion in its actiondescribed below and will return into engagement with the upper end ofcompensating bimetal element 34 when the breaker is tripped as shown inFIG. 3. In the closed condition of the breaker, a circuit is establishedfor current flow in a path extending from connectormember 28 throughbimetal element 26, conductors 42, contact finger 10, movable contact10a and stationary contact 14 to connector 14a.

To prevent ambient temperature variation from affecting the trippingpoint of the breaker for electrical conditions, element 34 is provided.For example, if the ambient temperature increases and causes bimetalelement 26 to bend to the right, compensating bimetal element 34correspondingly bends to the left to compensate for any movement ofarmature 32. In this manner, the thermal and magnetic conditions causedby current flow which are required to trip the breaker will remainconstant even it the surrounding temperature changes.

When excessive current flows through the breaker such as to causethermal tripping, bimetal element 26 bends. The lower end of suchbimetal element bears against the bottom of slot 22b to move slide plate22 in the righthand direction against the force of spring 24. Suchmovement of the slide plate causes the projections 22d on the left-handsides of slots 22c, FIG. 2, to move the lower end of armature 32 in theright-hand direction. Armature 32 carries compensating bimetal element34 with it to reduce the force applied to latch 8. And latch hook 36positively pulls latch 8 in the right-hand direction to separate thelatch from the catch. Because latch hook 36 biases latch 8 against theupper end portion of compensating bimetal member 34 and because slideplate 22 pulls armature 32 in the right-hand direction, the latch willrelease latch lever 6 when bimetal element 26 has bent the proper amountfrom an initial position as set by adjusting screw 30.

When suddent excessive current flows through the breaker such as tocause magnetic tripping, the high current flow through bimetal element26 induces a magnetic field whereby stationary polepiece 38 attractsarmature 32 thereto. As the armature is so attracted, it pushes slideplate 22 and compresses spring 24. There is suificient space in slot 22bin the slide plate between the armature and bimetal element 26 so thatthe latter will not be bent by such movement of the armature. When thearmature is attracted as aforesaid, it carries compensating bimetalelement 34 with it to decrease the force on the latch and carries latchhook 36 with it to pull latch 8 from catch 8b whereby to release latchlever 6.

When latch lever 6 is released due to either thermal or magnetictripping as aforesaid, Overcenter spring 12 pivots it clockwise. As aresult, the line of action of overcenter spring 12 is moved to the rightpast the pivot of contact finger 10 whereupon the Overcenter springsnaps the contacts open as shown in FIG. 4. The lower end of theright-hand depending leg of latch lever 6 strikes the cam surface ofcommon trip lever 20 to rotate the common trip lever clockwise. Thiscommon trip lever is rigidly coupled or connected to a like common triplever in the adjacent breaker to rotate it in unison. In such adjacentbreaker, the common trip lever moves the compensating bimetal element,latch hook and armature assembly to the right to trip the adjacentbreaker.

It will be apparent from FIGS. 1 and 4 that tripping of the breaker andclockwise rotation of latch lever 6 caused resetting spring 16 tostretch. In the transistory condition shown in FIG. 4, overcent'erspring 12 is under tension whereby it'causes the operating lever torotate clockwise from the on position shown in FIG. 1 toward the offposition shown in FIG. 3. Overcenter spring 12 becomes completelyconstricted before the operating lever moves all the Way off.Thereafter, resetting spring 16 returns latch lever 6 counterclockwise.Latch lever 6 carries spring 12 with it which in turn carries contactfinger with it to complete the clockwise rotation of the operating leverto its fully ofi? position shown in FIG. 3. It will be apparent thatduring the transitory condition shown in FIG. 4, catch 6a is below thelower end of latch 8. However, the resetting operation just describedcauses catch 6a to be raised and concurrently causes latch 8 to belowered below the catch as shown in FIG. 3. In this position, the latchis in condition to engage the catch when the operating lever is movedback to its on position provided the bimetal element 26 has cooled.

Whilethe apparatus hereinbefore described is effectively adapted tofulfill the objects stated, it is to be understood that we do not intendto confine our invention to the particular preferred embodiment ofelectric circuit breaker disclosed, inasmuch as it is susceptible ofvarious modifications without departing from the scope of theappendedclaims.

We claim:

1. In a circuit breaker having a spring-loaded latch tripped operatingmechanism mounted in an insulating housing and an operating leverextending from said housing'for actuating said operating mechanismbetween circuit-closed and circuit-open conditions:

(a) means for maintaining said operating mechanism in circuit-closedcondition when actuated thereto and for reliably tripping the same tocircuit-open condition in response to a predetermined electricalcondition comprising:

(b) latch means for said operating mechanism requiring application of aforce to maintain it latched;

(c) means for applying said force to said latch means to maintain saidoperating mechanism in circuitclosed condition;

(d) biasing means for applying an increasing counter force to said latchmeans to effect positive release of said operating mechanism when saidmaintaining force is decreased; 7

(e) and means responsive to an abnormal electrical condition fordecreasing said maintaining force to cause tripping of said operatingmechanism to circuit-open condition;

(f) said maintaining force applying means comprising and armatureassembly pivoted in said housing;

(g) a slide plate engaging a first portion of said arma ture and beingslidable in said housing;

(h) a spring compressed between said slide plate and a Wall of saidhousing to cause another portion of said armature assembly to apply saidforce to said latch means;

(i) and electro-responsive means for sliding said plate against theforce of said spring to cause said plate to pull said armature assemblyaway from said latch means to decrease said maintaining force.

2. The inventiondefined in claim 1, wherein:

(a) said biasing means comprises a resilient member rigidly secured atone end to the armature assembly and having another end extending to theother side of said latch means to separate the latter from saidoperating mechanism when the armature assembly is pulled away.

3. In a circuit breaker having a spring-loaded latchtripped operatingmechanism and an operating lever for actuating said operating mechanismbetween circuitclosed and circuit-open conditions:

(a) means for maintaining said operating mechanism in circuit-closedcondition and for electrically tripping the same to circuit-opencondition comprising:

(b) latch means requiring application of a force thereto to maintain itin latching engagement with said operating mechanism;

(c) means for applying said force to said latch means to maintain saidoperating mechanism in circuitclosed condition;

(d) biasing means for applying a counter force to said latch means whichis less than said maintaining force whereby said operating mechanismremains latched under normal electrical conditions;

(e) and means responsive to' an abnormal electrical condition fordecreasing said maintaining force and for creating and simultaneouslyand proportionally increasing said counter force to positively separatesaid latch means from said operating mechanism to trip the latter to itscircuit-open condition.

4. The invention defined in claim 1 wherein:

(a) said slide plate is provided with a slot opposite said spring havingone portion for pushing said armature assembly toward said latch means;

(b) and another portion of said slot engaging the other side of saidarmature assembly for pulling it away from said latch means under theforce of said electro-responsive means.

5. In a combined thermal and magnetic trip mechanism for an electriccircuit breaker; the combination comprising:

(a) an insulating housing;

(b) a stationary contact mounted in said housing and a movable contactfor engaging said stationary contact;

(c) an operating lever pivotally supported in said hous- (d) a springbiased trip mechanism comprising a movable contact carrying fingerpivoted on said operating lever, a latch lever pivoted in said housingand an overcenter spring connected between said movable contact carryingfinger and said latch lever;

I (e) a catch on said latch lever;

(f) a latch member pivoted on said operating lever for engaging saidcatch;

(g) a spring biased armature assembly for applying a force on said latchmember to maintain engagement with said catch and to maintain saidcontacts closed;

(h) combined electro-thermal and electromagnetic means for withdrawingsaid armature assembly to reduce the force applied to said latch member;

(i) and a latch hook on said armature assembly for pulling said latchmember from said catch when said armature is withdrawn to trip thecontacts open.

6. In a trip mechanism for an electric circuit breaker;

the combination comprising:

(a) an insulating housing having a stationary contact mounted thereinand a movable contact for engaging said stationary contact;

(b) a spring biased trip mechanism comprising a latch lever pivoted insaid housing and a movable contact carrying finger connected by anovercenter tension spring to said latch lever for opening and closingsaid contacts;

(c) an operating lever for actuating said trip mechanism;

(d) a catch on said latch lever;

(e) a latch member pivoted on said operating lever for engaging saidcatch;

(f) spring biased means in said housing comprising a compensatingbimetal member for applying a force on said latch memberto maintainengagement with said catch and to maintain said trip mechanism incontact-closed position;

(g) a resilient member mounted on said spring biased means for biasingsaid latch against said compensating bimetal member;

(h) and means responsive to an abnormal electrical condition forcounteracting said spring biased means whereby said resilient memberpulls said latch member from said catch to release said latch lever andto trip the contacts open.

7. In a circuit breaker, the combination of:

(a) a manual operating lever pivotally mounted in an insulating housing;

(b) a stationary contact in said housing;

(c) a movable contact carrier pivoted on said lever;

(d) a trip lever pivoted at a fixed point in said housing;

(e) an overcenter tension spring connected between said contact carrierand said trip lever;

(f) means mounted in said housing for holding said trip lever inunoperated position when said manual lever is in its on position tocause said overcenter spring to hold said contact carrier incontact-closed position; said means being responsive to movement of saidmanual lever to its off position to allow pivotal movement of said triplever thereby to carry the line of action of said overcenter spring andthe pivot of said contact carrier across one another and to cause saidovercenter spring to move said contact carrier to contact-open position,said means comprising:

(g) a pivoted latch member for holding said trip lever 8. in unoperatedposition when a force is applied to said latch member;

(h) spring biased means for applying a force to said latch member;

(i) means responsive to an excessive electrical con-' 8. In combinationwith a circuit breaker having an operating mechanism for operating thebreaker between circuit-closed and circuit-open conditions:

(a) an operating lever for actuating said operating mechanism;

(b) a catch on said operating mechanism;

(c) a movable latch for engaging said catch to maintain the breaker incircuit-closed condition and being separable from said catch to allowsaid operating mechanism to trip the breaker to circuit-open condition;

(d) means for applying a force to said latch to maintain it inengagement with said catch;

(e) means movable responsive to an abnormal current condition forincreasingly opposing the force of said force applying means as saidmovable means moves to reduce the force of said latch;

(f) and resilient means movable in response to movement of said movablemeans when said force is reduced for positively separating said latchfrom said catch to cause tripping of the breaker.

9. In combination with a circuit breaker of the type having a circuitbreaker operating mechanism for operating the breaker betweencircuit-closed and circuit-open conditions:

(a) an operating lever for actuating said operating mechanism;

(b) said operating mechanism comprising a catch thereon;

(c) a movable latch engaging said catch to maintain said breaker incircuit-closed condition and being separable from said catch to allowsaid operating mechanism to trip said breaker to circuit-open condition;

(d) means for applying a force to said latch to maintain the same inengagement with said catch;

(e) means responsive to an abnormal current condition for opposing saidforce applying means;

(f) and resilient means effective when said force is opposedsufiiciently for positively separating said latch from said catch tocause tripping of the breaker;

(g) said resilient means comprising a spring wire secured at one end tosaid force applying means and extending to the other side of said latchto pull said latch from said catch.

10. In a circuit breaker of the type having a circuit breaker operatingmechanism for operating the breaker between circuit-closed andcircuit-open conditions:

(a) an operating lever for actuating the breaker operating mechanism;

(b) an overcenter mechanism comprising a latch lever, means providing afixed pivot for said latch lever, a movable contact finger pivoted onsaid operating lever, an overcenter spring connected between said latchlever and said contact finger, and a latch pivoted on said operatinglever for engaging said latch lever;

(c) said latch and said contact finger being responsive to movement ofsaid operating lever for moving said latch lever and the pivot of saidcontact finger relative to one another against the force of saidovercenter spring whereby said over-center mechanism moves through itsdead center position to cause said contact finger to snap intocircuit-closed condition.

(d) a trip mechanism responsive to an abnormal electrical condition forcausing separation of said latch from said latch lever to cause trippingof the contact finger to circuit-open condition;

(e) and said trip mechanism comprising means to positively pull thelatch from the latch lever to release the latter.

11. In a circuit breaker having a spring-loaded latchtripped operatingmechanism and an operating lever for actuating said operating mechanismbetween circuitclosed and circuit-open conditions:

(a) means for maintaining said operating mechanism in circuit-closedcondition when actuated thereto and for positively tripping the same tocircuit-open condition in response to an abnormal electrical conditioncomprising:

(b) freely pivoted latch means for said operating mechanism requiringapplication of a force to maintain it latched;

(0) means for applying said force to said latch means to maintain saidoperating mechanism in circuitclosed condition;

open condition.

References Cited by the Examiner UNITED STATES PATENTS Gano et a1 20088Dorfman 20088 Dorfman et al 200116 Jennings 20088 Casey 20088 Norden20088 Coleman 200106 20 BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner.

1. IN A CIRCUIT BREAKER HAVING A SPRING-LOADED LATCHTRIPPED OPERATINGMECHANISM MOUNTED IN AN INSULATING HOUSING AND AN OPERATING LEVEREXTENDING FROM SAID HOUSING FOR ACTUATING SAID OPERATING MECHANISMBETWEEN CIRCUIT-CLOSED AND CIRCUIT-OPEN CONDITIONS: (A) MEANS FORMAINTAINING SAID OPERATING MECHANISM IN CIRCUIT-CLOSED CONDITION WHENACTUATED THERETO AND FOR RELIABLY TRIPPING THE SAME TO CIRCUIT-OPENCONDITION IN RESPONSE TO A PREDETERMINED ELECTRICAL CONDITIONCOMPRISING: (B) LATCH MEANS FOR SAID OPERATING MECHANISM REQUIRINGAPPLICATION OF A FORCE TO MAINTAIN IT LATCHED; (C) MEANS FOR APPLYINGSAID FORCE TO SAID LATCH MEANS TO MAINTAIN SAID OPERATING MECHANISM INCIRCUITCLOSED CONDITION; (D) BIASING MEANS FOR APPLYING AN INCREASINGCOUNTER FORCE TO SAID LATCH MEANS TO EFFECT POSITIVE RELEASE OF SAIDOPERATING MECHANISM WHEN SAID MAINTAINING FORCE IS DECREASED; (E) ANDMEANS RESPONSIVE TO AN ABNORMAL ELECTRICAL CONDITION FOR DECREASING SAIDMAINTAINING FORCE TO